Long-term effects on offspring of exposure of oocytes and embryos to chemical and physical agents.

Central to this review is the knowledge that, in some livestock species, the environment in which fertilization and embryo development occurs influences not only preimplantation embryo development but also the phenotype of resulting offspring. This knowledge is based on in-vitro studies where the induced changes in the embryo can result in an array of developmental abnormalities after transfer including fetal overgrowth. Whilst such findings are of immediate relevance to assisted reproduction in the human, they also raise another equally important but less obvious issue. Can the in-vivo environments in which fertilization and embryo development normally occur be influenced by exogenous factors (either physical or chemical) in such a way that long-term development is adversely affected? In a global environment of increased use of synthetic chemicals and increased production of pollutants, it is an issue of growing relevance. This review examines technical information that is pertinent to these issues together with a brief assessment of some possible molecular mechanisms responsible for aberrant development. The review concludes with an assessment of the clinical significance of the findings.